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Abstract

The small field-of-view (FOV) limitation of current coherent beam combiner technology is overcome, enabling beam combining over significantly larger fields of view. The system includes an input to receive an input wavefront, a local oscillator to generate a reference wavefront, and an optical combiner such as a beam splitter to combine the input wavefront and the reference wavefront to produce an output wavefront which is received by a detector. According to the invention, an optical element is supported to receive the reference wavefront and generate, in effect, a plurality of local oscillator point sources which provide a set of wavefronts that cover the required wider FOV. In the preferred embodiment, the optical element is a diffuser, and may optionally include a mechanism for rotating the diffuser to reduce speckle. In an alternative embodiment the optical element is a lenslet array. The spacing of the lenslets in the array is preferably such that the angle subtended by centers of two adjacent lenslets as seen from the center of the system's collimating lens or mirror is less than 0.83λ/D, where λ is the wavelength of the radiation, and D is the aperture diameter. This invention finds utility in any application which uses coherent beam combining, including optical communication systems, laser radar systems, and other fields of endeavor.

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First Claim